Transmitting data in a mobile communication system

ABSTRACT

According to one embodiment, a method for retransmitting a protocol data unit (PDU) in a mobile communication system includes: segmenting a first PDU to form one or more second PDUs if the first PDU does not fit within a PDU size indicated by a lower layer; and transmitting the one or more second PDUs to a receiving side. Segmenting the first PDU includes: mapping only a data field of the first PDU to a data field of the one or more second PDUs; and setting a header of each of the one or more second PDUs. The header of each of the one or more second PDUs includes a field indicating a sequence number of the first PDU.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/677,232, filed on Nov. 14, 2012, now U.S. Pat. No. 8,867,449, whichis a continuation of U.S. patent application Ser. No. 12/797,576, filedon Jun. 9, 2010, now U.S. Pat. No. 8,340,026, which is a continuation ofU.S. patent application Ser. No. 12/159,982, filed on Dec. 3, 2008, nowU.S. Pat. No. 8,428,086, which is the National Stage filing under 35U.S.C. 371 of International Application No. PCT/KR2007/000053, filed onJan. 4, 2007, which claims the benefit of earlier filing date and rightof priority to Korean Application No. 10-2006-0107103, filed on Nov. 1,2006, and also claims the benefit of U.S. Provisional Application Nos.60/757,063, filed on Jan. 5, 2006, 60/771,305, filed on Feb. 7, 2006,60/784,976, filed on Mar. 22, 2006, and 60/815,722, filed on Jun. 21,2006, the contents of which are all hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates to a mobile communication system, and moreparticularly, to transmitting data in the mobile communication system.

BACKGROUND ART

FIG. 1 is a structural diagram illustrating a Long Term Evolution (LTE)mobile communication system. The LTE system is an evolved version of aconventional Universal Mobile Telecommunications System (UMTS), and isbeing standardized under the 3rd Generation Partnership Project (3GPP)collaboration agreement.

An LTE network may be generally classified into an Evolved UMTSTerrestrial Radio Access Network (E-UTRAN) and a Core Network (CN). TheE-UTRAN includes at least one eNode-B serving as a base station. TheE-UTRAN also includes an Access Gateway (AG) located at the end of thenetwork so that it is connected to an external network.

The AG may be classified into a user-traffic processing unit and acontrol-traffic processing unit. In this case, a first AG for processingnew user traffic data may communicate with a second AG for processingcontrol traffic data via a new interface. A single eNode-B may includeat least one cell. A first interface for transmitting user traffic dataor a second interface for transmitting control traffic data may belocated between several eNode-Bs. The CN includes the AG and a pluralityof nodes for registering users of User Equipments (UEs). If required,another interface for discriminating between the E-UTRAN and the CN mayalso be used in the LTE network.

Two important elements of the LTE network are an eNode-B and a UE. Radioresources of a single cell include uplink radio resources and downlinkradio resources. The eNode-B allocates and controls the uplink anddownlink radio resources. In more detail, the eNode-B determines whichone of a plurality of UEs will use specific radio resources at aspecific time. After performing determination, the eNode-B informs thespecific UE of its decision, such that the eNode-B controls the UE toreceive the downlink data. For example, the eNode-B may allocate radioresources ranging from 100 MHz to 101 MHz to a specific UE (e.g., No. 1UE) after the lapse of a predetermined time of 3.2 seconds. Accordingly,the eNode-B may transmit downlink data to the No. 1 UE during a specifictime of 0.2 seconds after the lapse of the predetermined time of 3.2seconds.

In this way, the eNode-B determines which one of the plurality of UEswill perform uplink data transmission and the amount of radio resourcesthe UE can use at a specific time. Moreover, the eNode-B determines aduration of time the UE has to transmit the uplink data.

Compared with a conventional art Node-B or base station, theabove-mentioned eNode-B can effectively and dynamically manage radioresources. In the conventional art, a single UE is controlled tocontinuously use a single radio resource during a call connection time.However, considering the existence of a variety of recent services basedon Internet Protocol (IP) packets, the conventional art is ineffective.For example, most packet services have several intervals, wherein nodata is transmitted and no packets are generated during the callconnection time. Thus, if radio resources are continuously allocated toonly one UE, as in the conventional art, the allocation scheme is deemedineffective. In order to solve this and other problems, the E-UTRANsystem has been designed to allocate radio resources to a UE only whenthere is a need to use the UE, such as when service data is to betransmitted to the UE.

Uplink and downlink channels for transmitting data between the networkand the UE will hereinafter be described in detail. There exist downlinkchannels for transmitting data from the network to the UE, such as aBroadcast Channel (BCH) for transmitting system information, and adownlink Shared Channel (SCH) and downlink Shared Control Channel (SCCH)for transmitting user traffic data or control messages. The traffic dataor control messages of a downlink multicast service or broadcast servicemay be transmitted over the downlink shared channel (SCH), oradditionally over a Multicast Channel (MCH). Furthermore, there alsoexist uplink channels for transmitting data from the UE to the network,such as a Random Access Channel (RACH), and an uplink shared channel(SCH) and uplink shared control channel (SCCH) for transmitting usertraffic data or control messages.

FIG. 2 and FIG. 3 are conceptual diagrams illustrating a radio interfaceprotocol structure between the UE and the UMTS Terrestrial Radio AccessNetwork (UTRAN) based on a 3GPP radio access network standard.

The radio interface protocol horizontally includes a physical layer, adata link layer and a network layer. The radio interface protocolvertically includes a User Plane for transmitting data or informationand a Control Plane for transmitting a control signal (also called“signaling data”). The protocol layers shown may be classified into afirst layer (L1), a second layer (L2) and a third layer (L3) based onthree lower layers of a well-known interconnection scheme, such as anOpen System Interconnection (OSI) reference model.

The physical layer acting as the first layer (L1) provides anInformation Transfer Service over a physical channel. A radio resourcecontrol (RRC) layer located at the third layer (L3) controls radioresources between the UE and the network. For this purpose, the RRClayer exchanges RRC messages between the UE and the network. The RRClayer may be distributed to a plurality of network nodes (i.e., eNode-Band AG, etc.), and may also be located at the eNode-B or the AG.

A radio protocol control plane will hereinafter be described withreference to FIG. 2. The radio protocol control plane includes aphysical layer, a Medium Access Control (MAC) layer, a Radio LinkControl (RLC) layer, and a Radio Resource Control (RRC) layer.

The physical layer acting as the first layer (L1) transmits anInformation Transfer Service to an upper layer over a physical channel.The physical layer is connected to the Medium Access Control (MAC) layer(L2 layer) via a transport channel. The MAC layer communicates with thephysical layer such that data is communicated between the MAC layer andthe physical layer over the transport channel. Data may be communicatedamong different physical layers. Specifically, data is communicatedbetween a first physical layer of a transmission end and a secondphysical layer of a reception end.

The MAC layer of the second layer (L2) transmits a variety of servicesto the RLC (Radio Link Control) layer (L2 layer) over a logical channel.The RLC layer of the second layer (L2) supports transmission of reliabledata. A variety of functions of the RLC layer may also be implementedwith a function block of the MAC layer. In this case, no RLC layer isnecessary.

The RRC (Radio Resource Control) layer located at the uppermost part ofthe third layer (L3) is defined by the control plane only. The RRC layercontrols logical channels, transport channels, and physical channels inrelation to configuration, reconfiguration, and release operations ofRadio Bearers (RBs). Here, an RB is indicative of a service receivedfrom the second layer (L2) to implement data communication between theUE and the E-UTRAN. A radio protocol user plane will hereinafter bedescribed with reference to FIG. 3. The radio protocol user planeincludes the physical layer, the MAC layer, the RLC layer, and a PacketData Convergence Protocol (PDCP) layer.

The physical layer of the first layer (L1) and the MAC and RLC layers ofthe second layer (L2) are equal to those of FIG. 2. In order toeffectively transmit IP packets (e.g., IPv4 or IPv6) within a radiocommunication period having a narrow bandwidth, a PDCP layer of thesecond layer (L2) performs header compression to reduce the size of arelatively large IP packet header containing unnecessary controlinformation.

A detailed description of the RLC layer will hereinafter be described indetail. The principal functions of the RLC layer are for guaranteeing aQuality of Service (QoS) of each RB and transmitting data associatedwith the QoS. The RB service is indicative of a specific serviceprovided to an upper layer by the second layer of the radio protocol,such that all parts of the second layer affect the QoS. Specifically, itshould be noted that the second layer is greatly affected by the RLClayer. The RLC layer assigns an independent RLC entity to each RB toguarantee a unique QoS of the RB. In this case, the RLC entityconfigures an RLC protocol data unit (PDU) according to the size ofradio resources determined by a lower layer (i.e., the MAC layer).

Therefore, when transmitting the RLC PDU to the MAC layer, the RLCentity located at the eNode-B configures data having a predeterminedsize determined by the MAC entity, and transmits the RLC PDU to the MACentity. The RLC entity located at the UE also configures the RLC PDUaccording to the size of radio resources determined by the lower layer(i.e., the MAC layer). Therefore, when transmitting the RLC PDU to theMAC layer, the RLC entity located at the UE configures data having apredetermined size determined by the MAC entity, and transmits the RLCPDU to the MAC entity.

DISCLOSURE OF INVENTION

The present invention is directed to transmitting data in a mobilecommunication system.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method for transmitting data in a mobilecommunication system, the method comprising transmitting first data to areceiving side, receiving acknowledgment information for indicatingwhether the first data was successfully transmitted to the receivingside, if the first data was not successfully transmitted to thereceiving side, determining whether an amount of available radioresources is sufficient for retransmitting the first data to thereceiving side, retransmitting the first data to the receiving side ifthe amount of available radio resources is sufficient to retransmit thefirst data, reconfiguring the first data into at least one second dataif the amount of available radio resources is insufficient to retransmitthe first data, wherein the at least one second data can be transmittedto the receiving side using the amount of available radio resources, andtransmitting the at least one second data to the receiving side.

Preferably, the acknowledgment information is received from thereceiving side. Preferably, the acknowledgment information is receivedfrom a lower layer of a transmitting side.

In one aspect of the invention, the first data is a radio link controllayer protocol data unit (RLC PDU) comprising at least one of a sequencenumber (SN) field, a control/data/subframe (C/D/S) field, acomplete/partial (C/P) field, a following (F) field, and a lengthindicator (LI) field. Preferably, the control/data/subframe (C/D/S)field indicates whether the RLC PDU is the first data or second data.Preferably, the C/P field indicates how the RLC PDU is aligned to anupper layer service data unit (SDU).

In another aspect of the invention, the second data is a radio linkcontrol layer sub protocol data unit (RLC subPDU) comprising at leastone of a sequence number (SN) field, a control/data/subframe (C/D/S)field, a subframe sequence number (sSN) field, a remaining (RM) field, acomplete/partial (C/P) field, a following (F) field, and a lengthindicator (LI) field. Preferably, the sSN field indicates a sequentialorder of one of the at least one second data within a plurality oftransmitted second data related to the first data. Preferably, the RMfield indicates whether a subsequent second data exists after one of theat least one second data.

In a further aspect of the invention, the amount of available radioresources comprises a maximum amount of data scheduled to be transmittedto the receiving side.

In yet another aspect of the invention, a maximum amount of availableradio resources is indicated by scheduling information received from anetwork. Preferably, the scheduling information indicates timing andfrequency of the available radio resources.

In accordance with another embodiment of the present invention, anapparatus for transmitting data in a mobile communication systemcomprises means for transmitting first data to a receiving side, meansfor receiving acknowledgment information for indicating whether thefirst data was successfully transmitted to the receiving side, if thefirst data was not successfully transmitted to the receiving side, meansfor determining whether an amount of available radio resources issufficient for retransmitting the first data to the receiving side,means for retransmitting the first data to the receiving side if theamount of available radio resources is sufficient to retransmit thefirst data, means for reconfiguring the first data into at least onesecond data if the amount of available radio resources is insufficientto retransmit the first data, wherein the at least one second data canbe transmitted to the receiving side using the amount of available radioresources, and means for transmitting the at least one second data tothe receiving side.

Preferably, the acknowledgment information is received from thereceiving side. Preferably, the acknowledgment information is receivedfrom a lower layer of a transmitting side.

In one aspect of the invention, the first data is a radio link controllayer protocol data unit (RLC PDU) comprising at least one of a sequencenumber (SN) field, a control/data/subframe (C/D/S) field, acomplete/partial (C/P) field, a following (F) field, and a lengthindicator (LI) field.

In another aspect of the invention, the second data is a radio linkcontrol layer sub protocol data unit (RLC subPDU) comprising at leastone of a sequence number (SN) field, a control/datalsubframe (C/D/S)field, a subframe sequence number (sSN) field, a remaining (RM) field, acomplete/partial (C/P) field, a following (F) field, and a lengthindicator (LI) field.

In a further aspect of the invention, the amount of available radioresources comprises a maximum amount of data scheduled to be transmittedto the receiving side.

In yet another aspect of the invention, a maximum amount of availableradio resources is indicated by scheduling information received from anetwork. Preferably, the scheduling information indicates timing andfrequency of the available radio resources.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 is a structural diagram illustrating a Long Term Evolution (LTE)mobile communication system.

FIG. 2 is a diagram illustrating a control plane of a radio interfaceprotocol structure between a UE and a UMTS Terrestrial Radio AccessNetwork (UTRAN) based on a 3GPP radio access network standard.

FIG. 3 is a diagram illustrating a user plane of a radio interfaceprotocol structure between the UE and the UMTS Terrestrial Radio AccessNetwork (UTRAN) based on a 3GPP radio access network standard.

FIG. 4 is a diagram illustrating a method for constructing a MAC PDU inan RLC SDU in accordance with one embodiment of the present invention.

FIG. 5 is a structural diagram illustrating a MAC PDU format inaccordance with one embodiment of the present invention.

FIG. 6 is a flow chart illustrating a method for transmitting data of amobile communication system in accordance with one embodiment of thepresent invention.

FIG. 7 is a diagram illustrating a method for transmitting data of amobile communication system in accordance with one embodiment of thepresent invention.

FIG. 8 is a diagram illustrating a method for transmitting signals of amobile communication system in accordance with another embodiment of thepresent invention.

FIG. 9 is a diagram illustrating a method for transmitting signals of amobile communication system in accordance with another embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention relates to transmitting data in a mobilecommunication system.

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. A method fortransmitting data of a mobile communication system according to thepresent invention will hereinafter be described.

Prior to describing the present invention, it should be noted that thefollowing preferred embodiments of the present invention allow an RLClayer to reconfigure information received from an upper layer in theabove-mentioned hierarchical structure shown in the conventional art,and transmit the reconfigured information to the MAC layer. However, itis obvious to those skilled in the art that the scope of the presentinvention is not limited to only the above-mentioned RLC layer'stransmission case, and can also be applied to other examples. Firstinformation, transmitted from an upper layer and received by the RLClayer is referred to as an RLC service data unit (SDU). Secondinformation, which comprises the RLC SDU reconfigured by the RLC layerand transmitted to the MAC layer, is referred to as an RLC PDU. Thirdinformation, which comprises the RLC PDU reconfigured by the MAC layer,is referred to as a MAC PDU.

The RLC layer provides two RLC modes, i.e., an Unacknowledged Mode (UMor UM mode) and an Acknowledged Mode (AM or AM mode). The UM and AMmodes support different QoSs, such that a difference in operationmethods exists between them. Detailed functions of the UM and AM modesare also different from each other. Accordingly, the function of the RLClayer according to its operation modes will be described.

As a matter of convenience and better understanding of the presentinvention, the RLC in the UM mode is referred to as a UM RLC while theRLC in the AM mode is referred to as an AM RLC. The UM RLC attaches aPDU header including a sequence number (SN) to each PDU generated, andtransmits the resultant PDU equipped with the PDU header, such that areception end can recognize which one of a plurality of PDUs is lostduring transmission. Accordingly, the UM RLC preferably performstransmission of broadcast/multicast data or transmission of real-timepacket data (e.g., voice over Internet protocol (VoIP) or streaming) ofa Packet Service (PS) domain in a user plane. In a control plane, the UMRLC preferably performs transmission of a UM RRC message from among aplurality of RRC messages transmitted to a specific UE or specific UEgroup contained in a cell.

The AM RLC attaches the PDU header including the SN to each PDUgenerated in the same manner as the UM RLC; however, in contrast to theUM RLC, the AM RLC commands a reception end to acknowledge the PDUtransmitted from a transmission end. Accordingly, when performing thePDU acknowledgment, the reception end may request retransmission of anyPDU not received from the transmission end.

By utilizing the retransmission function, the AM RLC can guaranteetransmission of error-free data. Accordingly, the AM RLC performstransmission of non-real-time packet data such as a Transmission ControlProtocol/Internet Protocol (TCP/IP) of the PS domain in the user plane.In the control plane, the AM RLC performs transmission of an RRC messagerequiring an acknowledgement response (AM RRC message) from among aplurality of RRC messages transmitted to a specific UE contained in acell.

Directionally, the AM RLC is used for bi-directional communicationbecause a feedback signal is received from the reception end, whereasthe UM RLC is used for uni-directional communication. Preferably, thebi-directional communication is used for a point-to-point (PTP)communication, such that the AM RLC employs a dedicated logical channel.

Structurally, the UM RLC includes a single RLC entity comprising asingle transmission structure or a single reception structure. Incontrast, the AM RLC includes a single RLC entity comprising thetransmission structure and the reception structure. The AM RLC structureis more complex because of the retransmission function. In order tomanage the retransmission function, the AM RLC includes atransmission/reception buffer as well as a retransmission buffer, andperforms a variety of functions. The AM RLC functions comprise a usagefunction of a transmission/reception window for flow control, a pollingfunction for requesting status information from the reception end of apeer-RLC entity by the transmission end, a status report function forallowing the reception end to report its buffer state to thetransmission end of the peer-RLC entity, a status PDU function forcarrying status information, and a piggyback function for inserting astatus PDU in a data PDU to increase efficiency of data transmission,for example.

Additionally, if the AM RLC detects important errors during itsoperation, the AM RLC may perforin additional functions, such as a resetPDU function for requesting re-configuration of all operations andparameters from a counterpart AM RLC entity and a reset ACK PDU functionfor replying to the reset PDU, for example.

In order to support the above-mentioned functions, the AM RLC requires avariety of protocol parameters, status variables, and a timer. A varietyof PDUs used for the above-mentioned functions, such as the statusreport function, the status PDU function and the reset PDU function, aswell as PDUs for controlling AM RLC data transmission are referred to ascontrol PDUs. Other PDUs for transmitting user data are referred to asdata PDUs.

Preferably, the AM mode uses Automatic Repeat Request (ARQ) informationand the UM mode does not. Here, the ARQ information is indicative oftransmission/reception acknowledgement (ACK) information. Preferably,the transmission/reception ACK information indicates information relatedto a data block normally transmitted from the transmission end to thereception end, or other information related to an erroneous data blockabnormally transmitted from the transmission end to the reception end.

A representative example of an RLC PDU format for use in the UM mode isshown in Table 1.

TABLE 1 SN C/P F L1 F L1 . . . F RLC RLC . . . RLC SDU 1 SDU 2 SDU N

With reference to Table 1, a Sequence Number (SN) field indicates a dataflow of a corresponding RLC PDU, or indicates location information on alogical channel. A complete/partial (C/P) field indicates whether afirst data part of the RLC PDU is equal to a first part of an associatedSDU. The C/P field also indicates whether a last data part of the RLCPDU is equal to and end part of any associated SDUs.

For example, if the value of the C/P field is “00”, the beginning partof the PDU is equal to the beginning part of the SDU, and the end of thePDU is equal to the end of the SDU. If the value of the C/P field is“01”, the beginning part of the PDU is equal to the beginning part ofthe SDU, and the end of the PDU is not equal to the end of the SDU. Ifthe value of the C/P field is “10”, the beginning part of the PDU is notequal to the beginning part of the SDU, and the end of the PDU is equalthe end of the SDU. If the value of the C/P field is “11”, the beginningpart of the PDU is not equal to the beginning part of the SDU, and theend of the PDU is not equal to the end of the SDU.

A length indicator (LI) field indicates a boundary of an RLC SDU. Thus,if a single RLC PDU includes two RLC SDUs, the reception end canseparate between the RLC SDUs using the boundary information of the RLCSDU. A following (F) field indicates whether a next field is the LIfield or data.

Compared with the AM mode, the RLC PDU format of the UM mode need nottransmit/receive the transmission/reception acknowledgment information.Accordingly, the RLC PDU of the UM mode is simpler than the AM mode andcan have one header format. Moreover, if a transmission time point of acorresponding RLC PDU can be distinguished by a lower end according toretransmission information (i.e., redundancy-version information), thenthe SN field may be deleted.

A representative example of an ARQ RLC PDU format for transmission ofgeneral data in the AM mode is shown in Table 2.

TABLE 2 SN C/D/S C/P F LI F LI . . . F RLC RLC . . . RLC Control SDU 1SDU 2 SDU N PDU(opt)

A representative example of an ARQ RLC PDU format for transmission ofcontrol information (e.g., transmission/reception acknowledgmentinformation) in the AM mode is shown in Table 3.

TABLE 3 SN C/D/S Control PDU

Preferably, if the ARQ RLC PDU format of Table 2 cannot be transmittedto a destination without any change under the AM mode, an ARQ RLC subPDUis configured. Accordingly, a representative example of the ARQ RLCsubPDU is shown in Table 4.

TABLE 4 SN C/D/S sSN RM C/P F LI F LI . . . F RLC RLC . . . RLC ControlSDU 1 SDU 2 SDU N PDU(opt)

With reference to Tables 2, 3, and 4, the SN field, the C/P field, theLI field and the F field are equal to those of Table 1. Therefore, theirdetailed description will herein be omitted for convenience.

A Control/Data/Subframe (C/D/S) field indicates whether a correspondingRLC PDU is the ARQ RLC PDU, the ARQ RLC control PDU, or the ARQ RLCsubPDU. A subframe Sequence Number (sSN) field indicates locationinformation of a corresponding subPDU from among a plurality ofassociated subPDUs. A remaining (RM) field indicates the presence orabsence of associated subPDUs after the corresponding subPDU. In view ofthis, the ARQ RLC subPDU shown in Table 4 will be described in detailwith reference to the following preferred embodiments of the presentinvention.

FIG. 4 is a diagram illustrating a method for constructing a MAC PDU inan RLC SDU in accordance with one embodiment of the present invention.Preferably, the present invention is a method for constructing a dataunit in the RLC or MAC layer.

Referring to FIG. 4, the MAC layer of the UE receives informationindicating an amount of available radio resources from an eNode-B.Preferably, the MAC layer receives specific information indicating anamount of radio resources that can be used during a next transmissiontime from the eNode-B.

From the perspective of the eNode-B, the MAC layer of the eNode-Bdetermines whether downlink or uplink radio resources will be used. TheMAC layer of the eNode-B also determines the amount of radio resourcesthat will be allocated to individual UEs during a next transmissionperiod and informs the MAC layer of each UE of the determination. Byconsidering a plurality of data units stored in the UEs' buffers and apriority of the data units, each of the UEs determine the amount of datathat will be transmitted through each logical channel or from each RLCentity. In other words, each RLC entity determines the size of the RLCPDU to be transmitted to the MAC layer.

Accordingly, by considering an amount of downlink data of the UEs andpriority of each data, the MAC layer located at the eNode-B determinesthe amount of data that will be allocated to individual RLC entities,and informs each RLC of the determination. Each RLC then configures theRLC PDU according to the determination, and transmits the RLC PDU to theMAC layer.

Preferably, the MAC entity is connected to several RLC entities. EachRLC entity receives an RLC SDU from an upper layer, generates an RLC PDUby applying a command of the MAC layer to the received RLC SDU, andtransmits the generated RLC PDU to the MAC entity. The MAC entitycombines RLC PDUs received from individual RLC entities, configures thecombined RLC PDUs in the form of a single MAC PDU, and transmits thesingle MAC PDU to a physical layer.

In order to improve communication efficiency under the aforementionedsituation, it is preferable that the number of padding bits contained inthe MAC PDU or the RLC PDU be reduced. Preferably, a predeterminednumber of bits used for adjusting the size are reduced. For thisoperation, the MAC entity receives data from several logical channels(i.e., several RLC entities) and configures the MAC PDU using thereceived data.

However, in order to command the reception end to normally recover theRLC PDUs from the MAC PDU, specific information for indicating theamount of data contained in each logical channel is needed. Therefore,it is preferable to include information indicating an amount of datacorresponding to individual logical channels or other informationindicating identifiers (IDs) of the logical channels.

Preferably, the reception end extracts information of the RLC PDU usinga logical channel ID contained in the MAC PDU header and data-block sizeinformation of each logical channel. The reception end then transmitsthe extracted information to the corresponding RLC entities.

Operations of the MAC and RLC layers according to the present inventionwill hereinafter be described with further reference to FIG. 4. The MACPDU includes a MAC header and an RLC PDU. The RLC PDU includes data ofthe RLC SDU and segment information associated with the RLC SDU receivedfrom the upper layer. The segment information performs a functionsimilar to the RLC header. Preferably, the segment information includesboundary information of the RLC SDU in a single RLC PDU, for example.The MAC header indicates the size of each RLC PDU contained in the MACPDU and which one of a plurality of RLC entities or logic channelscorresponds to each RLC PDU.

If control information (e.g., status report information) for indicatinga reception status is contained in the MAC PDU, the control informationis contained in a single RLC PDU. Accordingly, the MAC header mayindicate the presence of the control information. In this case, thecontrol information may be exemplarily implemented with a method foremploying a logical channel ID having a special value.

FIG. 5 is a structural diagram illustrating a MAC PDU format inaccordance with one embodiment of the present invention. Preferably, theMAC PDU is based on the RLC PDU received from an upper RLC entity.

Referring to FIG. 5, an RLC ID field indicates that a corresponding RLCPDU has been received over a specific logical channel or from a specificRLC entity. A Length field indicates the size of each RLC PDU. The Ffield indicates whether following values are acquired by a combinationof the RLC ID field, the Length field and the F field or whether thefollowing values are real RLC PDUs.

Notably, data may be unexpectedly lost over physical channels ofcommunication systems. Compared to the conventional system, the physicallayer of a UTRAN system can more correctly transmit data from thetransmission end to the reception end. However, the probability of datatransmission error is not completely removed from the UTRAN system.Specifically, the longer the distance from the UE to the eNode-B, thehigher the data loss rate of the UE.

Therefore, the communication system of the present invention requires aspecial management method such as when TCP data requires error-freetransmission or signaling data. Accordingly, the communication systemmay use the AM mode. With regard to a TCP packet, the size of the TCPpacket can be extended to 1500 bytes. Therefore, if the TCP packetconfigured in the form of the RLC SDU is transmitted to the RLC, the RLCentity can recombine the TCP packet within a specific size allowed by alower layer (i.e., MAC layer) and transmit the recombined TCP packet toa destination.

Several RLC PDUs generated by the above-mentioned recombination aretransmitted to the reception end via the physical layer. However, if atleast one RLC PDU corresponding to a single RLC SDU is not received inthe reception end, the reception end informs the transmission end of RLCPDU non-reception. In this case, if the transmission end retransmits anentire RLC SDU associated with the lost RLC PDU, a large amount of radioresources may be wasted.

For example, the RLC SDU of 1500 bytes is divided into ten RLC PDUs,each of which has 150 bytes. If a single RLC PDU from among the 10 RLCPDUs is not correctly received in the reception end, the entire RLC SDUis retransmitted according to the above-mentioned situation.Accordingly, a data amount of 1400 bytes is unnecessarily wasted. Inthis case, there is a need to perform the retransmission at the RLC PDUlevel.

Wireless environments provided when the RLC PDU is to be retransmittedmay be different from those during initial transmission of the RLC PDU.For example, if the RLC PDU is initially transmitted, a correspondingRLC entity can transmit data of 200 bytes during a unit time. However,when the RLD PDU is retransmitted, a corresponding RLC entity mayunexpectedly transmit data of only 50 bytes during the unit time. Inthis case, the RLC PDU cannot be retransmitted without change.Specifically, the RLC PDU having an original format cannot beretransmitted to a desired destination. In order to solve this problem,one embodiment of the present invention divides the original RLC PDUinto several RLC subPDUs. Preferably, the present invention allows atransmission end to receive reception status information from thereception end after the transmission end transmits the RLC PDU.Thereafter, the transmission end performs retransmission according tothe radio resources presently allocated to the transmission end.

FIG. 6 is a flow chart illustrating a method for transmitting signals ofa mobile communication system in accordance with one embodiment of thepresent invention. Referring to FIG. 6, the transmission end transmitsfirst data of the RLC PDU to the reception end (S60). The reception endreceives the first data and transmits the transmission/receptionacknowledgment information (e.g., ACK/NACK signals) of the RLC PDU andreception status information for the received first data (S61).

If the first data is to be retransmitted, the transmission enddetermines which one of a plurality of RLC PDUs was not received by thereception end using the transmission/reception acknowledgmentinformation received from the reception end. Thereafter, thetransmission end recognizes an amount of radio resources available forthe retransmission (S62).

If the RLC PDU can be retransmitted using the available amount of radioresources, the RLC PDU is retransmitted (S63). However, if the RLC PDUcannot be retransmitted using the available amount of radio resources,the RLC PDU is reconfigured in the form of two or more RLC subPDUs(S64), such that the RLC subPDUs can be transmitted using the availableamount of radio resources (S65).

In other words, if the RLC PDU data is required to be retransmitted, andan amount of radio resources allocated to the transmission end is lessthan the size of the initial RLC PDU, the transmission end reconfiguresthe RLC PDU in the form of two or more RLC subPDUs (S64), and transmitsthe RLC subPDUs to the reception end (S65). Preferably, each RLC entityconfigures a predetermined size of radio resources allocated by thelower layer.

The amount of radio resources is indicative of a maximum amount of datacapable of being transmitted from the transmission end. The transmissionend also includes a transmission-end RLC.

If there is a need to reconfigure the RLC PDU using schedulinginformation or other information loaded in the transmission/receptionacknowledgment information, the RLC PDU is reconfigured in the form oftwo or more RLC subPDUs such that the RLC subPDUs can be transmitted tothe reception end. The transmission end can also reconfigure the RLC PDUin the form of two or more RLC subPDUs on the condition that any one ofthe transmitted RLC PD Us does not arrive at the reception end.

In one aspect of the invention, the scheduling information ortransmission/reception acknowledgment information received at thereception end from the transmission end indicates the size of the RLCsubPDUs reconfigured by the transmission end. Preferably, the schedulinginformation is transmitted from the eNode-B to the UE for indicatingwhich one of a plurality of UEs will-use a predetermined size of radioresources during a predetermined time. Specifically, the schedulinginformation indicates size information of radio resources to be used bya determined UE, and time information to be used by the determined UEaccording to the radio resources having the size information.

Preferably, the transmission/reception acknowledgment information istransmitted from the reception end to the transmission end forindicating the correct reception of one of a plurality of PDUs or SDUsat the reception end. The transmission/reception acknowledgmentinformation also indicates the non-reception of one of the plurality ofPDUs or SDUs at the reception end. The reception end recognizes whethera received data block is the RLC PDU or the RLC subPDU. If the receptionend can not recognizes, the reception end reassembles an RLC SDU bybinding non-related data in a single bundle. Otherwise, the order ofdata units contained in the single RLC SDU may be changed from anoriginal order.

In order to distinguish between the RLC PDU and the RLC subPDU, anadditional field capable of discriminating between the RLC PDU and theRLC subPDU may be added to a header part of a data block communicatedbetween the RLC and MAC. According to the value of the additional field,the RLC of the reception end can determine whether the data blockreceived from the lower MAC layer is the RLC PDU or the RLC subPDU. Inthis way, when transmitting the data block to the lower MAC layer, theRLC entity of the transmission end determines whether its transmissiondata is the RLC PDU or the RLC subPDU, and can properly establish aPDU/subPDU discriminator for the header part of the data block.

Preferred embodiments of the RLC subPDUs will hereinafter be describedwith reference to the drawings. Notably, the following RLC subPDUsformats are not limited to the preferred embodiments of the presentinvention, and can also be applied to other examples as necessary.

FIG. 7 is a diagram illustrating a method for transmitting data of amobile communication system in accordance with one embodiment of thepresent invention. Referring to FIG. 7, a first block 70 includes threeIP packets. Preferably, the three IP packets are considered RLC SDUsfrom the viewpoint of the RLC entity. Preferably, sizes of individual IPpackets for use in one embodiment of the present invention are 500 bits,600 bits and 300 bits, respectively.

A second block 71 indicates how to configure the RLC PDUs using thethree IP packets. Here, it is assumed that the allowed sizes of the RLCPDUs under wireless environments at initial transmission are 300 bits,400 bits and 700 bits, respectively. Moreover, an RLC PDU includesseveral header fields.

A detailed description of individual header fields in accordance withthe present invention is as follows. A Flow ID (Queue ID) fieldindicates which one of a plurality of RBs or which one of a plurality ofRLC entities is associated with the RLC PDU. Indeed, a single UEincludes several RBs having different QoSs and characteristics orseveral RLC entities having different QoSs and characteristics.Therefore, the Flow ID field discriminates an individual RB from otherRBs.

A Transmission Sequence Number (TSN) field helps rearrange or manageretransmission of the received RLC PDUs. Preferably, the TSN valueincreases by a specific value “1” whenever a new RLC PDU is generated.Thus, the TSN indicates the order of individual RLC PDUs in a single RLCentity.

A Length Indicator (LI) field indicates a boundary of an RLC SDU. Thus,if a single RLC PDU includes two RLC SDU parts, a reception end canproperly separate between the RLC SDUs using the boundary information ofthe RLC SDU.

A third block 72 indicates how to reconfigure the RLC PDU in the form ofRLC subPDUs. When a reception end informs a transmission end ofnon-reception of a specific RLC PDU using an ARQ operation, thetransmission end is required to retransmit the RLC PDU. However, at aspecific time at which the retransmission is required, an amount ofradio resources available for use by a lower layer of the transmissionend may be insufficient for transmitting the RLC PDU. Accordingly, it ispreferable to divide the RLC PDU into RLC subPDUs, or reconfigure theRLC PDU in the form of RLC subPDUs, such that the RLC subPDUs can betransmitted to the reception end using the available radio resources.

Referring to FIG. 7, a method for reconfiguring a second RLC PDU of thesecond block 71 in the form of a plurality of RLC subPDUs willhereinafter be described. Here, it is assumed that the amount of datacapable of being transmitted during a unit time based on wirelessenvironments when retransmitting from a lower end (or lower layer) is100 bits, 200 bits and 100 bits, respectively. Therefore, the RLC PDU tobe retransmitted is configured in the final of RLC subPDUs to which 100bits, 200 bits and 100 bits are sequentially assigned.

Preferably, the transmission end informs the reception end of atransmission when transmitting the RLC PDU or RLC subPDUs. Thus, todistinguish the RLC subPDUs from the RLC PDU, the LI field having aspecific value may be used. In FIG. 7, a special LI field is used duringtransmission of an RLC subPDU. Therefore, whenever the reception endreceives the special LI field, the reception end determines that thereceived data block is an RLC subPDU, and performs operationsaccordingly.

Generally, the reception end uses the LI field to determine the boundaryof an RLC SDU. However, if the reception end receives a RLC PDU with aLI field set to specific value, the reception end regards the receivedRLC PDU as RLC SubPDU. In that case, to identify the original RLC PDUassociated with the received RLC subPDU, the TSN field of the RLCsubPDUs is set to the same value as the TSN field of the original RLCPDU. Therefore, the reception end can recognize location information ofthe received RLC subPDUs, associated RLC PDUs or associated RLC SDUs.

Accordingly, if a single RLC PDU is divided into several RLC subPDUs,additional information is required in order for a reception end todetermine the order of the received RLC subPDUs. Thus, a subPDU infofield is preferably used for this purpose.

The subPDU info field indicates whether a specific RLC subPDU is locatedat an end part of its associated RLC PDU and relative locationinformation of the specific RLC subPDU among associated RLC subPDUs. Forexample, referring to the third block 72 of FIG. 7, the subPDU infofield of the third RLC subPDU indicates that the particular RLC subPDUis a final RLC subPDU associated with the RLC PDU, and that theparticular RLC subPDU is the third RLC subPDU among RLC subPDUsassociated with the RLC PDU.

Although the RLC subPDUs are retransmitted from the transmission end tothe reception end as described above, the reception end may notcorrectly receive some parts of the RLC subPDUs. Accordingly, the RLCsubPDUs may be further divided into lower data blocks. However, if theprobability of losing all of the RLC PDU and associated RLC subPDUs isextremely low, it is preferable that a RLC subPDU is not furtherdivided.

FIG. 8 is a diagram illustrating a method for transmitting data of amobile communication system in accordance with one embodiment of thepresent invention. Referring to FIG. 8, a first block 80, a second block81 and a third block 82 are structurally similar to the first, secondand third block of FIG. 7. However, additional fields are depicted inFIG. 8.

A subframing indicator (S) field indicates that the received data blockis RLC subPDU of an RLC PDU. Preferably, if the S field is set to “Y”,then a corresponding data block is an RLC subPDU.

A length extension indicator (LEX) field indicates whether a next fieldis an LI field or an RLC SDU. If the LEX field is set to “Y”, then thenext field is the LI field. A subPDU info field is used when a receptionend rearranges the RLC subPDUs.

FIG. 9 is a diagram illustrating a method for transmitting data of amobile communication system in accordance with one embodiment of thepresent invention. Referring to FIG. 9, a first block 90, a second block91 and a third block 92 are structurally similar to the first, secondand third block of FIGS. 7 and 8. However, additional fields aredepicted in FIG. 9.

A sequence number (SN) field indicates data flow of a corresponding RLCPDU or location information on a logical channel. Acontrol/data/subframe (C/D/S) field indicates whether a correspondingRLC PDU is an ARQ RLC PDU for data transmission, an ARQ RLC control PDUfor transmitting control information, or an ARQ RLC subPDU reconfiguredwhen the ARQ RLC PDU is retransmitted.

A complete/partial (C/P) field indicates whether a first data part ofthe PDU is equal to a first part of an associated SDU. The C/P fieldalso indicates which one of a plurality of SDUs corresponds to an end ofthe RLC PDU. An exemplary case, wherein the C/P field comprises two bitsis as follows.

For example, if the value of the C/P field is “00”, a beginning part ofthe PDU is equal to a beginning part of the SDU, and an end of the PDUis equal to an end of the SDU. If the value of the C/P field is “01”, abeginning part of the PDU is equal to a beginning part of the SDU, andan end of the PDU is not equal to an end of the SDU. If the value of theC/P field is “10”, a beginning part of the PDU is not equal to abeginning part of the SDU, and an end of the PDU is equal an end of theSDU. If the value of the C/P field is “11”, a beginning part of the PDUis not equal to a beginning part of the SDU, and an end of the PDU isnot equal to an end of the SDU.

A following (F) field indicates whether a next field is the LI field ordata. The length indicator (LI) field indicates a boundary of an SDUcontained in the PDU. A subframe Sequence Number (sSN) field indicateslocation information of a specific subPDU from among a plurality ofassociated subPDUs. A remaining (RM) field indicates the presence orabsence of associated subPDUs after the specific subPDU.

As apparent from the above description, the present invention provides amethod for transmitting data of a mobile communication system. If aspecific data block is to be retransmitted but sufficient radioresources for transmitting the data block are not provided, the presentinvention reconfigures the data block in order to transmit the datablock using the available radio resources. Preferably, the presentinvention retransmits only what is necessary. Therefore, datatransmission efficiency is increased and service disconnection time of auser or UE is reduced.

Although the present invention is described in the context of mobilecommunication, the present invention may also be used in any wirelesscommunication systems using mobile devices, such as PDAs and laptopcomputers equipped with wireless communication capabilities. Moreover,the use of certain terms to describe the present invention should notlimit the scope of the present invention to certain type of wirelesscommunication system, such as UMTS. The present invention is alsoapplicable to other wireless communication systems using different airinterfaces and/or physical layers, for example, TDMA, CDMA, FDMA, WCDMA,etc.

The preferred embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.).

Code in the computer readable medium is accessed and executed by aprocessor. The code in which preferred embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentinvention, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

Industrial Applicability

The present invention can be applied to a mobile communication system.

What is claimed is:
 1. A method for transmitting protocol data unit(PDU) by an apparatus in a mobile communication system, the methodcomprising: segmenting a first PDU to form one or more second PDUs ifthe first PDU does not fit within a size of PDU indicated by a lowerlayer, wherein the first PDU includes one or more first service dataunits (SDUs) and each of the one or more second PDUs includes one ormore SDUs; and transmitting the one or more second PDUs to a receivingapparatus, wherein the segmenting the first PDU to form the one or moresecond PDUs comprises mapping only the one or more first SDUs to the oneor more second PDUs and setting a header of each of the one or moresecond PDUs, and wherein, if at least one second PDU includes more thanone second SDUs, the more than one second SDUs belong to different firstSDUs.
 2. The method of claim 1, wherein the header of each of the one ormore second PDUs includes a field indicating a sequence number of thefirst PDU.
 3. The method of claim 1, wherein the header of each of theone or more second PDUs includes a field indicating a position of acorresponding second PDU within the first PDU.
 4. The method of claim 1,wherein the header of each of the one or more second PDUs includes afield indicating whether a corresponding second PDU is a last segmentedPDU within the first PDU or not.
 5. The method of claim 1, wherein theheader of each of the one or more second PDUs includes a fieldindicating that a corresponding second PDU is segmented.
 6. The methodof claim 1, wherein the first PDU is an Acknowledge Mode Data (AMD) PDU.7. An apparatus for transmitting protocol data unit (PDU) in a mobilecommunication system, the apparatus is configured to: segment a firstPDU to form one or more second PDUs if the first PDU does not fit withina size of PDU indicated by a lower layer, wherein the first PDU includesone or more first service data units (SDUs) and each of the one or moresecond PDUs includes one or more SDUs; and transmit the one or moresecond PDUs to a receiving apparatus, wherein the apparatus maps onlythe one or more first SDUs to the one or more second PDUs and sets aheader of each of the one or more second PDUs, and wherein, if at leastone second PDU includes more than one second SDUs, the more than onesecond SDUs belong to different first SDUs.
 8. The apparatus of claim 7,wherein the header of each of the one or more second PDUs includes afield indicating a sequence number of the first PDU.
 9. The apparatus ofclaim 7, wherein the header of each of the one or more second PDUsincludes a field indicating the position of a corresponding second PDUwithin the first PDU.
 10. The apparatus of claim 7, wherein the headerof each of the one or more second PDUs includes a field indicatingwhether a corresponding second PDU is a last segmented PDU within thefirst PDU or not.
 11. The apparatus of claim 7, wherein the header ofeach of the one or more second PDUs includes a field indicating that acorresponding second PDU is segmented.
 12. The apparatus of claim 7,wherein the first PDU is an Acknowledge Mode Data (AMD) Protocol DataUnit (PDU).